Touch screens are present in many different types of common modern electronic devices, such as cellular telephones, tablet computers, portable music and video devices, personal digital assistants, portable gaming devices, and so on. In these electronic devices the touch screen is part of the user interface of the device. The touch screen typically includes a display, touch sensors, and a touch controller. The touch sensors are typically some sort of transparent sensor array, such as an ultrasonic, resistive, vibration, or capacitive sensor array, that is attached to or formed as an integral part of the display. When a user touches the sensor array either with a finger or a stylus, for example, the sensor array generates corresponding electronic sensor signals that are provided to the touch controller. From these sensor signals, the touch controller determines the type of “touch event” along with various characteristics of the touch event, and provides this information to processing circuitry in the electronic device. The processing circuitry operates in response to this information to allow a user to control the electronic device or an application running on the processing circuitry through these touches of the touch screen.
The touch controller typically captures frame data from the touch sensors and processes this frame data to determine the type of touch event that has occurred on the touch screen. This processing is typically referred to as touch frame processing and through this processing the touch controller determines the type of touch event and the location of the touch event on the touch screen. The touch controller must detect and report (to the processing circuitry) different types of touch events, such as when a user initially touches the touch screen, when the user has stopped touching the touch screen, and when a touch is moving on the touch screen, and when a moving touch has stopped moving.
Common touch screen device includes a touch sensor, a touch controller and a display. The touch sensor is a user interface device integrated with a panel which, when touch with a finger or stylus, produces signals from which the controller can determine touch event and its touch properties (position, size, pressure etc). The transparent sensor is usually mounted onto the display so that the output can be directly seen by the user together with the device's graphical user interface, thus allowing direct interaction. For example, the user can select a button object on the display screen by directly touching the button on the display. The device application program can determine which object was touched using the information generated by the sensor and reported by the controller. Many hand-held devices such as smart phones, personal digital assistants (PDAs), media players, tablet computers and similar devices include touch screens. As more and more interactive and advanced user applications are developed for these devices, more and more information has to be generated and decoded by the touch controller.
Touch controllers also typically provide high-level functionality, such as gesture recognition, descriptive touch data, shape recognition, the definition of multiple touch areas on the touch screen, single touch or multiple touch detection, and so on. Such high-level functionality requires a lot of information be transferred between the touch controller and the touch sensor and between the touch controller and the processing circuitry. While it is desirable to provide such high-level functionality for applications running on the processing circuitry that utilize such high-level functions, not all applications utilize all or in some cases any of these high-level functions.
There is a need for improved filtering of touches in order to eliminate or lower the unnecessary transfer of information relating to high-level functionality for applications that do not utilize such high-level functions.